This is what I have learned from second and third hand experience with saltwater.
Once set up, saltwater and freshwater will cost around the same (metal halides do take up a ton of energy though), although the up front costs for saltwater are generally higher, but with leds, the gap is closing.
Saltwater fish are generally more sensitive, as most of them (don't quote me on this) are still wild caught, so small fluctuations in the system can cause large consequences (moreso than freshwater). Because of this, fish tend to be a lot more expensive, and flakes usually aren't an option
Saltwater is a bit more maintenance than most freshwater, but would be similar to a high tech planted setup: adding salt to r/o and getting the hardness correct as opposed to dosing/measuring ferts in the water and removing limiting nutrients
Color-wise, I would say that saltwater tends to have more colorful fish in general, but this shouldn't be a deciding factor, as there is a ton of colorful FW
fish, and in many cases, they can be even more colorful than SW
I tend to like plants more than coral, although one thing I eventually want to try is seahorsies